1. Field of the invention
The present invention is generally concerned with torsional damper devices comprising at least two coaxial parts mounted to rotate relative to one another within a defined range of relative angular movement against circumferentially acting elastic means disposed circumferentially between them.
2. Description of the prior art
As is known, this type of torsional damper device is normally incorporated in the design of a friction clutch, particularly for automotive vehicles, for example, in which case one coaxial part comprises a friction disk designed to rotate with a first shaft, in practice a driving shaft, the motor output shaft in the case of an automotive vehicle, constituting a part refered to hereinafter for convenience as the driving part, whereas the other of said coaxial parts is carried on a hub design to rotate with a second shaft, in practice a driven shaft, the gearbox input shaft in the case of an automotive vehicle, constituting a part referred to hereinafter for convenience as the driven part.
This type of torsional damper device is used to permit regulated transmission of rotational torque applied to one of its coaxial parts where the other is itself subject to a rotational torque, in other words, to filter vibrations which may arise at any point in the kinematic system in which it is incorporated, extending from the motor to the axles in the case of an automotive vehicle.
The present invention is more particularly directed to the case where the circumferentially acting elastic means disposed between the driving part and the driven part in the circumferential direction comprise at least one block of elastic material extending in a substantially tangential direction relative to a circumference of the damper and partially housed, without circumferential clearance in a rest configuration of the damper, in an opening formed for this purpose in a first of said coaxial parts, and partially housed, with circumferential clearance in said rest configuration and for at least a first circumferential direction, in an opening formed for this purpose in a second of said coaxial parts and having at least one elastic material peg projecting from its corresponding circumferential end in said first circumferential direction, this circumferential end being at least partly covered by a distribution and retaining plate, usually of sheet metal, formed with an opening through which said elastic material peg passes.
This is the case, for example, in the torsional damper device which is the subject of French patent application No. 82 02034 filed Feb. 9 1982, now Publication No. 2,521,244, of Aug. 12, 1983.
In the rest configuration of the assembly, the elastic material peg carried by an elastic material block extends circumferentially beyond the distribution and retaining plate through which it passes.
On relative angular movement of the two coaxial parts concerned, it offers the advantage of progressively increasing the stiffness of the circumferentially acting elastic means operative between said coaxial parts before the elastic material block which carries it comes into action in its turn.
In practice, the coaxial part in which the elastic material block is housed with circumferential clearance in the rest configuration of the assembly comprising only one flange, a hub disk, for example, whereas the other comprises two transverse flanges, guide rings, for example, disposed one on each side of the former, the elastic material peg lies substantially in the median transverse plane of the assembly, so that said hub disk can act on it through its edge, said guide rings acting conjointly, by their edge, on the elastic material block, on opposite sides of said peg.
In the French patent application mentioned hereinabove, the elastic material peg extends along the axis of the elastic material block which carries it, being at the center of the corresponding circumferential end of the latter, with the result that the distribution and retaining plate through which it passes is of generally circular annular configuration, constituting a closed loop, the opening in the distribution and retaining plate for said elastic material peg to pass through being itself generally in the center of the plate.
An arrangement of this kind is generally satisfactory.
However, it may prove wanting in certain specific applications, in particular when the torque to be transmitted from the driving part to the driven part is relatively high.
In this case, deterioration of the distribution and retaining plate may sometimes be observed.
The explanation for this may be found in the fact that, being in its center, the opening in it for the elastic material peg to pass through significantly reduces the bearing surface area which it presents to the hub disk after circumferential crushing of said elastic material peg.
A general objective of the present invention is to provide an arrangement whereby this disadvantage may be overcome and other advantages secured.